The invention relates to re-machining a generator rotor tooth dovetail and, more particularly, to reducing stresses resulting from partial slot dovetail re-machining.
Severe galling or pitting of field dovetail load surfaces, mis-machining, or other causes may require re-machining of a new partial slot length dovetail in order to restore their required load bearing surface contact. Special fitting is then necessary to install oversized wedges in a transition zone between the newly cut load surface and the original load surface. The stresses in the transition zone and for several inches on either side of the transition zone may have unacceptably high stresses on either the rotor tooth or wedge, resulting in a possible reduction of fatigue life.
It would be desirable to reduce the stresses in the wedge and tooth such that partial slot dovetail machining can be implemented without sacrificing the fatigue life of the parts involved.
A conventional process of partial slot dovetail re-machining has been to fit wedges to “overhang” the transition zone, with the butt joint between wedges being lined up to the middle of the transition zone. When the transition zone gets too long, the tooth and wedge stresses become unacceptably high, and the re-machined dovetail would need to extend the length of the rotor body.